1. Technical Field
This invention relates to an image forming apparatus in which an AC bias and a DC bias are applied to charge a photoreceptor uniformly in a contact charging method or a close proximity charging method having the operation principle of discharging, and more particularly, to a measuring technique of film thickness of the photoreceptor.
2. Related Art
Various members such as a charging roller, developing brash, and transferring roller, cleaning brush, cleaning blade, and the like physically come into contact with a surface of a photoreceptor of the image forming apparatus. Such physical contact gradually abrades away a surface of a photoconductive layer along with the repeated image forming process. In particular, the magnitude of sliding frictional forces applied by the cleaning brush or cleaning blade is strong enough to cause the abrasion of the photoconductive layer.
With the afore-described abrasion, if the thickness of the photoconductive layer is reduced by a certain amount, the photosensitivity will significantly degrade or the charging characteristics will be deteriorated. This makes it impossible to charge the surface of the photoreceptor uniformly at a desired potential, and a clear image cannot be formed.
Therefore, the thickness of the photoconductive layer of the photoreceptor is measured as time goes on to estimate the operating life of the photoreceptor.